1. Field of the Invention
The present invention relates to computer systems using core logic circuits as a bus bridge(s) to interface a central processor(s), video graphics processor, memory and input-output peripherals together, and more particularly, in utilizing the same core logic circuits as a bus bridge for an accelerated graphics port(s) and/or a Fibre Channel Arbitrated Loop interface(s).
2. Description of the Related Technology
Use of computers, especially personal computers, in business and at home is becoming more and more pervasive because the computer has become an integral tool of most information workers who work in the fields of accounting, law, engineering, insurance, services, sales and the like. Rapid technological improvements in the field of computers have opened up many new applications heretofore unavailable or too expensive for the use of older technology mainframe computers. These personal computers may be used as stand-alone workstations (high end individual personal computers) or linked together in a network by a "network server" which is also a personal computer which may have additional features specific to its purpose in the network. The network server may be used to store massive amounts of data, and may facilitate interaction of the individual workstations connected to the network for electronic mail ("E-mail"), document databases, video teleconferencing, whiteboarding, integrated enterprise calendar, virtual engineering design and the like. Multiple network servers may also be interconnected by local area networks ("LAN") and wide area networks ("WAN").
A significant part of the ever increasing popularity of the personal computer, besides its low cost relative to just a few years ago, is its ability to run sophisticated programs and perform many useful and new tasks. Personal computers today may be easily upgraded with new peripheral devices for added flexibility and enhanced performance. A major advance in the performance of personal computers (both workstation and network servers) has been the implementation of sophisticated peripheral devices such as video graphics adapters, local area network interfaces, SCSI bus adapters, full motion video, redundant error checking and correcting disk arrays, and the like. These sophisticated peripheral devices are capable of data transfer rates approaching the native speed of the computer system microprocessor central processing unit ("CPU"). The peripheral devices' data transfer speeds are achieved by connecting the peripheral devices to the microprocessor(s) and associated system random access memory through high speed expansion local buses. Most notably, a high speed expansion local bus standard has emerged that is microprocessor independent and has been embraced by a significant number of peripheral hardware manufacturers and software programmers. This high speed expansion bus standard is called the "Peripheral Component Interconnect" or "PCI." A more complete definition of the PCI local bus may be found in the PCI Local Bus Specification, revision 2.1; PCI/PCI Bridge Specification, revision 1.0, PCI System Design Guide, revision 1.0; and PCI BIOS Specification, revision 2.1, the disclosures of which are hereby incorporated by reference. These PCI specifications are available from the PCI Special Interest Group, P.O. Box 14070, Portland, Oreg. 97214.
A computer system has a plurality of information (data and address) buses such as a host bus, a memory bus, at least one high speed expansion local bus such as the PCI bus, and other peripheral buses such as the Small Computer System Interface (SCSI), Extension to Industry Standard Architecture (EISA), and Industry Standard Architecture (ISA). The microprocessor(s) of the computer system communicates with main memory and with the peripherals that make up the computer system over these various buses. The microprocessor(s) communicates to the main memory over a host bus to memory bus bridge. The peripherals, depending on their data transfer speed requirements, are connected to the various buses which are connected to the microprocessor host bus through bus bridges that detect required actions, arbitrate, and translate both data and addresses between the various buses.
Increasingly sophisticated microprocessors have revolutionized the role of the personal computer by enabling complex applications software to run at mainframe computer speeds. The latest microprocessors have brought the level of technical sophistication to personal computers that, just a few years ago, was available only in mainframe and mini-computer systems. Some representative examples of these new microprocessors are the "PENTIUM" and "PENTIUM PRO" (registered trademarks of Intel Corporation). Advanced microprocessors are also manufactured by Advanced Micro Devices, Digital Equipment Corporation, Cyrix, IBM and Motorola.
These sophisticated microprocessors have, in turn, made possible running complex application programs using advanced three dimensional ("3-D") graphics for computer aided drafting and manufacturing, engineering simulations, games and the like. Increasingly complex 3-D graphics require higher speed access to ever larger amounts of graphics data stored in memory. This memory may be part of the video graphics processor system, but, preferably, would be best (lowest cost) if part of the main computer system memory. Intel Corporation has proposed a low cost but improved 3-D graphics standard called the "Accelerated Graphics Port" (AGP) initiative. With AGP 3-D, graphics data, in particular textures, may be shifted out of the graphics controller local memory to computer system memory. The computer system memory is lower in cost than the graphics controller local memory and is more easily adapted for a multitude of other uses besides storing graphics data.
The proposed Intel AGP 3-D graphics standard defines a high speed data pipeline, or "AGP bus," between the graphics controller and system memory. This AGP bus has sufficient bandwidth for the graphics controller to retrieve textures from system memory without materially affecting computer system performance for other non-graphics operations. The Intel 3-D graphics standard is a specification which provides signal, protocol, electrical, and mechanical specifications for the AGP bus and devices attached thereto. This specification is entitled "Accelerated Graphics Port Interface Specification Revision 1.0," dated Jul. 31, 1996, the disclosure of which is hereby incorporated by reference. This AGP specification is available from Intel Corporation, Santa Clara, Calif.
The AGP interface specification uses the 66 MHz PCI (Revision 2.1) as an operational baseline, with three performance enhancements to the PCI specification which are used to optimize the AGP specification for high performance 3-D graphics applications. These enhancements are: 1) pipelined memory read and write operations, 2) demultiplexing of address and data on the AGP bus by use of sideband signals, and 3) data transfer rates in excess of 500 megabytes per second ("MB/sec.") using the AGP 2x mode. The remaining AGP specification does not modify the PC 2.1 Specification, but rather provides a range of graphics-oriented performance enhancements for use by the 3-D graphics hardware and software designers. The AGP specification is neither meant to replace nor diminish full use of the PCI standard in the computer system. The AGP specification creates an independent and additional high speed local bus for use by 3-D graphics devices such as a graphics controller, wherein the other input-output ("I/O") devices of the computer system may remain on any combination of the PCI, SCSI, EISA and ISA buses.
To functionally enable this AGP 3-D graphics bus, new computer system hardware and software are required. This requires new computer system core logic designed to function as a host bus/memory bus/PCI bus to AGP bus bridge meeting the AGP specification, and new Read Only Memory Basic Input Output System ("ROM BIOS") and Application Programming Interface ("API") software to make the AGP dependent hardware functional in the computer system. The computer system core logic must still meet the PCl standards referenced above and facilitate interfacing the PCI bus(es) to the remainder of the computer system. This adds additional costs to a personal computer system, but is well worth it if 3-D graphics are utilized. Some personal computer uses such as a network server do not require 3-D graphics, but would greatly benefit from having a Fibre Channel Arbitrated Loop (FC-AL) interface, more fully described hereinbelow, for connecting to input-output devices such as high performance and storage capacity multiple disk drives, high-bandwidth networking, and the like. The FC-AL has the ability to address up to 126 devices and store up to 1.1 Terabytes of data per loop, with data transfer rates reaching 200 Megabytes per second (MB/sec) using dual loops and having cabling distances from 30 meters to 10 kilometers.
AGP and PCI devices serve different purposes and the respective interface cards (e.g., AGP 3-D video controller and PCI NIC) are not physically interchangeable even though there is some commonality of signal functions between the AGP and PCI interface specifications. While AGP capabilities are very desirable in a personal computer utilizing 3-D graphics, it is wasteful and redundant for those personal computers not requiring 3-D capabilities. The cost/performance (i.e., flexibility of the computer for a given price) of a personal computer is of paramount importance for commercial acceptance in the market place. In today's competitive computer industry, technical performance alone does not guarantee commercial success. Technical performance of any personal computer product must be maximized while constantly reducing its manufacturing costs. To achieve a high performance to cost ratio, commonality of components and high volume of use are key factors. Thus, commonality of components such as logic circuits, printed circuit boards, microprocessors, computer boxes and power supplies, will drive the costs down for both workstations and servers. Also the high end workstations and network servers would benefit if one generic model of a personal computer could be effectively used in either capacity. Further benefits in reducing costs may be realized by using common components in portable and desktop (consumer and low end business) computers.
Faster and more sophisticated microprocessors are here now or will soon be introduce in the near future. The Digital Equipment Corporation "ALPHA" processor runs in excess of 400 MHz and the still in development, Intel Corporation's 64 bit data and address bus width processors (code name Merced) will soon be available for use in high end computer servers. As processor speeds continue to increase, and practical multi-processor hardware and operating system software is multiplying this ever increasing data processing power. I/O speeds and memory storage capacity must match the processor performance or the processors will be starved of data.
Fibre Channel has been proposed as a solution for high speed data transfer and has been widely accepted in the computer industry. Fibre Channel is a 1 gigabit per second (or faster) data transfer interface technology that provides a general transport vehicle for Upper Level Protocols (ULPs) such as Intelligent Peripheral Interface (IPI) and Small Computer System Interface (SCSI) command sets, the High-Performance Parallel Interface (HIPPI) data framing, Internet Protocol (IP), IEEE 802.2, Asynchronous Transfer Mode (ATM), and the like. The Fibre Channel technology merges high-speed I/O and networking functionality into one connectivity technology. Fibre Channel is an integrated set of standards established by the American National Standards Institute (ANSI) X3T11 for both network and channel I/O interfaces, and these ANSI Fibre Channel Standards are hereby incorporated by reference. The Fibre Channel Standards (FCS) include, but are not limited to: FC-PH, FC-PH-2, physical and signaling interfaces; FC-FG, FC-SW, FC-GS, fabric requirements and generic services; FC-AL, arbitrated loop topology; FC-IG, implementation guidance; FC-SB, FC-FP, FC013 Disk, FC-13 Tape, FC-LE, SCSI-FCP, SCSI-GPP and FC-ATM are FC-4 documents; FC-AE, commercial and military avionics applications.
The FCS define high-speed data transfer interfaces that can be used to connect together workstations, mainframes, supercomputers, storage devices and displays. These standards address the need for very fast transfers of large volumes of information and may relieve system manufacturers from the burden of supporting the variety of channels and networks currently in place, as it provides unified standards for networking, storage and data transfer. The Fibre Channel standards are organized into the following levels:
FC-0 defines the physical portions of the Fibre Channel including the fibre, connectors, and optical and electrical parameters for a variety of data rates and physical media. Coax and twisted pair versions are defined for limited distance applications. FC-0 provides the point-to-point physical portion of the Fibre Channel. A variety of physical media is supported to address variations in cable plants. PA1 FC-1 defines the transmission protocol which includes the serial encoding, decoding, and error control. PA1 FC-2 defines the signaling protocol which includes the frame structure and byte sequences. PA1 FC-3 defines a set of services which are common across multiple ports of a node. PA1 FC-4 is the highest level in the Fibre Channel standards set. It defines the mapping, between the lower levels of the Fibre Channel and the IPI and SCSI command sets, the HIPPI data framing, IP, and other Upper Level Protocols (ULPs).
Of these levels, FC-0, FC-1, and FC-2 are integrated into the FC-PH document. The Fibre Channel protocol provides a range of implementation possibilities extending from minimum cost to maximum performance. The transmission medium is isolated from the control protocol so that each implementation may use a technology best suited to the environment of use. These standards are more fully defined in ANSI X3.230-1994, Fibre Channel Physical and Signaling Interface (FC-PH) Rev 4.3, available from the American National Standards Institute, 11 W. 42.sup.nd Street, New York, N.Y. 10036, and are hereby incorporated by reference.
What is needed is an apparatus, method, and system for a personal computer that provides at least one AGP interface connected to at least one AGP bus and a Fibre Channel Arbitrated Loop (FC-AL) interface, or two or more FC-AL interfaces utilizing multiple use high production volume logic and interface circuits having the capability of providing an FC-AL and/or an AGP interface(s).